Quickness of Movement in the Snatch
It is reasonable to suggest that all good exponents of the Snatch display two performance attributes. Firstly, they demonstrate quickness of movement as they descend under the bar and, secondly, they display a deep and stable receiving position. However, this article will discuss a hidden third attribute.
In general, photography and videography provide the coach and the athlete with an ample opportunity to study receiving positions, and to see and evaluate expert performance. However, the ability to assess an athlete’s quickness of movement presents a more difficult problem. It requires a greater sophistication of technology and procedure, and a significant input of time. Whereas there is a plethora of scholarly studies on the mechanics of the pull, there are extremely few that have investigated athlete movement speed. As a result, there is paucity of knowledge about this aspect of skill, and it receives far less attention from coaches and athletes.
My lack of knowledge in this area was greatly improved by a fortuitous meeting with Daniel Gahreman who was then a lecturer at Charles Darwin University. He showed me his Sony Cybershot RX10 Mark 2 camera which had the capability to record video at 100 frames per second. Furthermore, he extolled the virtue of extracting frames from a video recording to form a sequence of photos. At first, I did not see how a sequence of photos could be better than simply viewing the video itself. However, that soon changed. If the video is captured in good lighting, the sharpness of extracted frames is excellent and this allows the opportunity to study movement to a degree that was previously unachievable. The key, of course, is the frame rate of the video and at 100 frames per second, it means that every photo in the sequence is 1/100th second apart. This allows an effective measurement of the interval between key moments in the performance. For example, it becomes possible to quantify the time interval between moments A, B and C in Figure 1 below.
The fall of the bar
The purpose of the following illustration is to show the fall of the bar from the moment it reaches maximum elevation, until the moment it is arrested by the lifter. The illustration was traced as accurately as possible from frames extracted from a video recorded at 100 frames per second by a Sony Cybershot RX10 Mark 2. The performance took place in a national championship and was a successful third attempt.
Table 1: Explanation of Illustration
|The last video frame in which the athlete has contact with the ground. After this video frame, the athlete is airborne. This position can be described as the “finish of the pull” even though the athlete will still have upward force on the bar as they drop.
|The frame of the video in which the bar is judged to have arrived at its maximum elevation (or apex). After this moment, the bar begins to fall.
|The frame of the video in which the bar reaches its lowest point in the receiving position. At this point the moment the athletes arrests the downward movement of the bar completely.
Knowing that a full size weight plate has a diameter of 45cm, readers can approximate the distance that the bar falls with the naked eye. This distance (marked as “buffer”) is approximate to or less than one quarter the diameter of the weight plates. A later unpublished study using 3D motion analysis led by Daniel Gahreman, accurately quantified the fall of the bar for this athlete, Zac Millhouse, at 7.9 cm from apex of pull to overhead lockout, and a further fall of 5.1cm result from compression (squashing) of the lifter.
The need for quickness of movement
Knowledge of how far the bar drops before it is arrested by the athlete helps us to appreciate the importance of speed of movement under the bar. It’s obvious that, for each and every athlete, there must be a limit for how far the bar can drop before it becomes impossible to squeeze under it. Furthermore, it is not just a matter of the distance of the drop but also the time the athlete has at their disposal. If an athlete has a “buffer” of 10cm of less (see figure 1), they must move fast into position or the bar will fall too low for success to be possible.
Table 2 will assist you appreciate how a bar accelerates to ground if it is in true free fall. In the first 1/10th second, the bar drops 4.9 cm but a doubling of this time to 2/10th second results in a bar drop of 19.6 cm. In other words, 1/10th second difference in an athlete’s speed of drop under the bar makes a substantial difference.
However, the bar is not in true free fall. Even though the athlete is moving rapidly downwards under the bar and their feet are not touching the ground, they will still apply some upward force to the bar using their arms. This upward force has two effects. Firstly it slows the fall of the bar, and secondly it accelerates the downward movement of the athlete. This is an excellent example of Newton’s Third Law of Motion – “Every action has an equal and opposite reaction”.
Table 2: Free Fall due to Gravity
|Distance of Fall (cm)
Athletes tend to show significant differences in their movement speed under the bar in Olympic movements. The most plausible factor is how well they can apply force on the bar during the descent. If an athlete is considered to be extremely quick under the bar, it must be because they apply considerable force to the bar using their arms. This action is often referred to as the pull under. It is an aspect of skill which may or may not evolve without the need for any deliberate training strategy or coaching intervention. However, quickness of movement is much more likely to evolve if appropriate skill drills and exercises are prescribed and it becomes a deliberate coaching strategy.
It is a fact that 1/10th second difference in athlete movement speed matters a great deal.